The present invention relates generally to a method for manufacturing hinges and more particularly to a method for manufacturing vehicle door hinges.
Vehicle door hinges are typically made from two hinge parts pivotable with respect to one another about a hinge pin. One of the hinge parts is securely mounted to a door and the other to the vehicle body, so that the door can pivot about the hinge pin between an opened and closed position. The typical process for manufacturing both of the hinge parts is a stamping process. The stamping process, although widely used in the production of vehicle hinge parts, is expensive compared with other production methods because it entails significant waste of material. When high quality materials are used for the parts, the cost of the wasted material can be significant. Casting has also been used to manufacture hinge parts of this type, though casting is also an expensive production process for hinges of this type.
In many vehicle hinges, both hinge parts are shaped so that the hinge pin passes perpendicularly through holes drilled in the stamped metal hinge parts. In other vehicle hinges, at least one of the hinge parts is shaped to include a sleeve for receiving the hinge pin longitudinally. For example, one known horizontal axis hinge for a lift gate includes a hinge part stamped from a strip of metal approximately 6 mm thick. During the manufacturing process, a bent portion is formed by stamping an end of the strip of metal around to form a hook, so that the edge almost abuts against the flat section of the strip to form a sleeve for receiving the hinge pin. The edge of the strip of metal is welded to the flat section of the strip at the end of the hook. The inside of the hook portion is machined out to form an inside diameter for fitting the hinge pin, which passes longitudinally through the hook.
A vehicle door hinge faces certain forces during use. For example, for vertical axis hinges for vehicle side doors, the weight of the door and any other vertical forces placed on the door, particularly in the opened position, create forces on the hinge that may cause deflection of the hinge, such as a vertical deflection, or sag. In addition, when the door is in its fully opened position and an additional force in the opening direction is placed on the door, a torque about the axis of the hinge is created. This situation, referred to as an over-open condition, may cause an angular deflection in the hinge.